Fracking
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EPA 816-R-04-003
Chapter 4 Hydraulic Fracturing Fluids
Chapter 4 Hydraulic Fracturing Fluids
This chapter summarizes the information EPA collected on the types and volumes of fracturing fluids and additives that may be used for hydraulic fracturing of coalbed methane wells. This chapter also provides EPA’s evaluation of the fate and transport of fracturing fluids that are injected into targetedcoal layers during the hydraulic fracturing process. This evaluation was conducted to provide the Agency with information on whether a Phase II study is warranted. Captioned photographs in this chapter show the use of fracturing fluids at a coalbed methane well (Figures 4-1 through 4-11 at the end of this chapter). 4.1 Introduction
The types and use of fracturing fluids have evolved greatly overthe past 60 years and continue to evolve. The U.S. oil and gas industry has used fluids for fracturing geologic formations since the early 1940s (Ely, 1985). The Handbook of Stimulation Engineering (Ely, 1985), a comprehensive history of the evolution of hydraulic fracturing fluids in the oil and gas industry, was used as a source of information for this chapter. In addition, EPA identifiedfluids and fluid additives commonly used in hydraulic fracturing through literature searches, reviews of relevant MSDSs provided by service companies, and discussions with field engineers, service company chemists, and state and federal employees. Available scientific literature indicates that hydraulic fracturing fluid performance became a prevalent research topic in the late 1980s and the 1990s. Mostof the literature pertaining to fracturing fluids relates to the fluids’ operational efficiency rather than their potential environmental or human health impacts. There is very little documented research on the environmental impacts that result from the injection and migration of these fluids into subsurface formations, soils, and USDWs. Some of the existing literature does offer informationregarding the basic chemical components present in most of these fluids. The composition of fracturing fluids and additives is discussed in detail in the next section. The main goal of coalbed hydraulic fracturing is to create a highly conductive fracture system that will allow flow through the methane-bearing coal zone to the production well used to extract methane (and groundwater). Hydraulicfracturing fluids are used to initiate and/or expand fractures, as well as to transport proppant into fractures in coalbed formations. Proppants are sand or other granular substances injected into the formation to hold or “prop” open coal formation fractures created by hydraulic fracturing. The viscosity of fracturing fluids is considered when they are formulated, to provide for efficient transport andplacement of proppant into a fracture. Most of the fracturing
Evaluation of Impacts to Underground Sources of Drinking Water by Hydraulic Fracturing of Coalbed Methane Reservoirs June 2004 4-1
EPA 816-R-04-003
Chapter 4 Hydraulic Fracturing Fluids
fluids injected into the formation are pumped back out of the well along with groundwater and methane gas (see section 3.3 in Chapter 3 for a moredetailed discussion of fracturing fluid recovery). 4.2 Types of Fracturing Fluids and Additives
Service companies have developed a number of different oil- and water-based fluids and treatments to more efficiently induce and maintain permeable and productive fractures. The composition of these fluids varies significantly, from simple water and sand to complex polymeric substances with a multitudeof additives. Each type of fracturing fluid has unique characteristics, and each possesses its own positive and negative performance traits. For ideal performance, fracturing fluids should possess the following four qualities (adapted from Powell et al., 1999):
• • • •
Be viscous enough to create a fracture of adequate width. Maximize fluid travel distance to extend fracture length. Be able...
Chapter 4 Hydraulic Fracturing Fluids
Chapter 4 Hydraulic Fracturing Fluids
This chapter summarizes the information EPA collected on the types and volumes of fracturing fluids and additives that may be used for hydraulic fracturing of coalbed methane wells. This chapter also provides EPA’s evaluation of the fate and transport of fracturing fluids that are injected into targetedcoal layers during the hydraulic fracturing process. This evaluation was conducted to provide the Agency with information on whether a Phase II study is warranted. Captioned photographs in this chapter show the use of fracturing fluids at a coalbed methane well (Figures 4-1 through 4-11 at the end of this chapter). 4.1 Introduction
The types and use of fracturing fluids have evolved greatly overthe past 60 years and continue to evolve. The U.S. oil and gas industry has used fluids for fracturing geologic formations since the early 1940s (Ely, 1985). The Handbook of Stimulation Engineering (Ely, 1985), a comprehensive history of the evolution of hydraulic fracturing fluids in the oil and gas industry, was used as a source of information for this chapter. In addition, EPA identifiedfluids and fluid additives commonly used in hydraulic fracturing through literature searches, reviews of relevant MSDSs provided by service companies, and discussions with field engineers, service company chemists, and state and federal employees. Available scientific literature indicates that hydraulic fracturing fluid performance became a prevalent research topic in the late 1980s and the 1990s. Mostof the literature pertaining to fracturing fluids relates to the fluids’ operational efficiency rather than their potential environmental or human health impacts. There is very little documented research on the environmental impacts that result from the injection and migration of these fluids into subsurface formations, soils, and USDWs. Some of the existing literature does offer informationregarding the basic chemical components present in most of these fluids. The composition of fracturing fluids and additives is discussed in detail in the next section. The main goal of coalbed hydraulic fracturing is to create a highly conductive fracture system that will allow flow through the methane-bearing coal zone to the production well used to extract methane (and groundwater). Hydraulicfracturing fluids are used to initiate and/or expand fractures, as well as to transport proppant into fractures in coalbed formations. Proppants are sand or other granular substances injected into the formation to hold or “prop” open coal formation fractures created by hydraulic fracturing. The viscosity of fracturing fluids is considered when they are formulated, to provide for efficient transport andplacement of proppant into a fracture. Most of the fracturing
Evaluation of Impacts to Underground Sources of Drinking Water by Hydraulic Fracturing of Coalbed Methane Reservoirs June 2004 4-1
EPA 816-R-04-003
Chapter 4 Hydraulic Fracturing Fluids
fluids injected into the formation are pumped back out of the well along with groundwater and methane gas (see section 3.3 in Chapter 3 for a moredetailed discussion of fracturing fluid recovery). 4.2 Types of Fracturing Fluids and Additives
Service companies have developed a number of different oil- and water-based fluids and treatments to more efficiently induce and maintain permeable and productive fractures. The composition of these fluids varies significantly, from simple water and sand to complex polymeric substances with a multitudeof additives. Each type of fracturing fluid has unique characteristics, and each possesses its own positive and negative performance traits. For ideal performance, fracturing fluids should possess the following four qualities (adapted from Powell et al., 1999):
• • • •
Be viscous enough to create a fracture of adequate width. Maximize fluid travel distance to extend fracture length. Be able...
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